RUTHENIUM ZIRCONIUM COMPLEXES CONTAINING C2 BRIDGES WITH BOND ORDERS OF 3, 2, AND 1 - SYNTHESIS AND STRUCTURES OF CP(PME3)2RUCHNCHNZRCLCP2 (N = 0, 1, 2)

A series of Ru/Zr complexes linked by C2 bridges of bond orders 3, 2, and 1 were prepared, and characterized by spectroscopic data and single-crystal X-ray diffraction. The dimetalloalkyne complex Cp(PMe3)2RuC = CZrClCp2 was prepared by the reaction of Cp(PMe3)2RuC = CH with either Cp2Zr(CH3)Cl or Cp2Zr(NMe2)Cl. This dimetalloalkyne is the first example of a structurally characterized alkyne that is substituted by an electron-rich metal at one end, and by an electron-deficient metal at the other. The reaction of Cp(PMe3)2RuC = CH with [Cp2Zr(H)Cl]n gives the dimetalloalkene complex Cp(PMe3)2RuCH = CHZrClCp2, which has a three-center, two-electron agostic interaction between the Zr and the vinylic CH that is beta to Zr. Carbonylation of Cp(PMe3)2RuCH = CHZrClCp2 with 1 atm of CO produces the eta-2-acyl complex Cp(PMe3)2RuCH = CHC(O)ZrClCp2. Analysis of the spectroscopic and structural data for this acyl compound indicates a substantial contribution from a zwitterionic resonance form that has a formal positive charge at Ru and a negative charge on the Zr portion. Hydrolysis of Cp(PMe3)2RuCH = CHZrClCp2 produces the known zirconium complex [Cp2ZrCl]2O and the ruthenium vinyl complex Cp(PMe3)2RuCH = CH2. Reaction of [Cp2Zr(H)Cl]n with Cp(PMe3)2RuCH = CH2 gives the dimetalloalkane complex Cp(PMe3)2RuCH2CH2ZrClCp2. Spectroscopic and crystallographic data are interpreted to indicate that this compound also has an agostic interaction between the Zr and a CH adjacent to Ru.